Apparatus for moving a pair of opposing surfaces in response to an electrical activation

ABSTRACT

An apparatus for moving a pair of opposing surfaces in response to an electrical activation having a support including a rigid non-flexing portion, at least one pivotable arm portion extending from the rigid non-flexing portion, a pair of opposing surfaces with one opposing surface on the at least one pivotable arm portion for movement relative to one another, and a force transfer member operably positioned for driving the at least one pivotable arm portion in rotational movement. An actuator is operably engaged between the rigid portion and the force transfer member to drive the force transfer member in movement relative to the rigid portion to pivot the at least one pivotable arm portion with a loss of motion of less than 40% in response to an electrical activation of the actuator.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 10/845,943 filed on May 14, 2004, which is adivisional application of U.S. patent application Ser. No. 10/067,762filed on Feb. 6, 2002.

FIELD OF THE INVENTION

The present invention relates to an apparatus for moving a pair ofopposing surfaces in response to an electrical activation.

BACKGROUND OF THE INVENTION

Various types of piezoelectric devices are known to those skilled in theart. Many of these devices include complex configurations and are veryexpensive to manufacture. Other devices include simpler configurations,but are extremely limited in the corresponding maximum range of movementor the corresponding maximum application of force.

In such known devices, when the piezoelectric actuator is electricallyactivated, the rectangular prism geometry of the device expandspredominantly along a predetermined axis. When the piezoelectric deviceis deactivated, the geometry of the device contracts predominantly alongthe predetermined axis. This expansion and contraction of thepiezoelectric device can be used to operate an apparatus, e.g. to openand close a clamp or valve. An apparatus for clamping or valvingtypically includes a support having two members spaced with respect toeach other. The piezoelectric device is transversely disposed betweenthe two spaced members. As the piezoelectric device expands in a lineardirection, the members are driven or pivoted along a curvilinear path.The pivoting of the members along a curvilinear path results in aninefficient transfer of force from the piezoelectric device to thesupport. The piezoelectric actuator in most known configurations ispositioned parallel to the desired motion providing little opportunityto select different hinge axis locations and/or structuralconfigurations to optimize performance.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for moving a pair ofopposing surfaces in response to an electrical activation. The apparatusincludes a support including a rigid non-flexing portion, first andsecond pivotable arm portions extending from the rigid portion, a pairof opposing surfaces with one opposing surface on each pivotable armportion for movement relative to one another, and a force transfermember operably positioned between the first and second pivotable armportions. An actuator is operably engaged between the rigid non-flexingportion and the force transfer member to drive the force transfer memberin movement along a fixed path causing at least one of the first andsecond pivotable arm portions to pivot in response to an electricalactivation of the actuator. The support and force transfer elements ofthe structure are designed to be rigid, non-flexing elements. Anyunplanned flexing can reduce the effective life of the mechanism, andreduces the amount of force transferred through the hinge axes to pivotthe arms. The reduction in force limits the displacement and force ofthe pivoting arms. The selection of the hinge axis location andcorresponding structural configuration allows substantial capability tooptimize the performance of the apparatus for the particularapplication.

The piezoelectric actuator can be preloaded with force when installed inthe support element. For example, the piezoelectric actuator can beclamped within the support structure with an adjustable screw supportingone end allowing optimal force preloading. An adjustable screwconfiguration is easy to use and allows a large degree of adjustability.Preloading the piezoelectric actuator in any suitable fashioncontributes to maximum efficiency of force transfer during actuation,and allows fine tuning of the initial position of the apparatus prior toactuation of the piezoelectric element. Preloading can also ensure thatthe piezoelectric actuator maintains contact with the apparatus atopposite ends throughout the range of expansion and contraction. The useof a threaded adjustment screw for preloading enables assembly withoutrequiring adhesives or other means of securely connecting thepiezoelectric actuator at opposite ends to the apparatus, and avoids thepossibility of damaging tension or torsional moments on thepiezoelectric actuator. The threaded adjustment screw allows simplecompensation for dimensional variations in the piezoelectric actuatorduring assembly to the support.

Other applications of the present invention will become apparent tothose skilled in the art when the following description of the best modecontemplated for practicing the invention is read in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a perspective view of one embodiment of an apparatus formoving a pair of opposing surfaces in response to an electricalactivation having a support and an actuator in accordance with thepresent invention;

FIG. 2 is a side view of the apparatus of FIG. 1 with the actuatordeactivated;

FIG. 3 is an exaggerated side view of the apparatus of FIG. 1 with theactuator partially activated;

FIG. 4 is an extremely exaggerated side view of the apparatus of FIG. 1with the actuator fully activated;

FIG. 5 is a second embodiment of the apparatus with the supportincluding a force transferring member having an alternative shape;

FIG. 6 is a third embodiment of the apparatus with the support includingan adjustable seat;

FIG. 7 is a simplified flow chart illustrating the process of optimizingthe flex axis of the present invention; and

FIG. 8 is a set of separate intersecting curves showing force versusdisplacement for the mechanical support and the piezoelectric elementaccording to a process of the present invention for optimizing the hingegeometry of the mechanical support.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a perspective view of one embodiment of an apparatus 10 havinga support 12 and an actuator 14 in accordance with the presentinvention. The support 12 includes a rigid, non-flexible portion 16, atleast one pivotable arm portion, such as first and second pivotable armportions 18 and 20 extending from the rigid portion 16, a pair ofopposing surfaces 22 and 24 with one opposing surface 22, 24 on eachpivotable arm portion 18, 20 for movement relative to one another, and aforce transfer member 26 operably positioned between the first andsecond pivotable arm portions 18 and 20. Preferably, the support 12 is aunitary, integral, single-piece body. The actuator 14 is operablyengaged between the rigid, non-flexible portion 16 and the forcetransfer member 26 to drive the force transfer member 26 linearlycausing the first and second pivotable arm portions 18, 20 to pivotabout corresponding axes and drive the opposing surfaces 22 and 24 apartor away from each other with a loss of motion of less than 40% inresponse to an electrical activation from a controller 28 incommunication with the actuator 14.

When activated, the actuator 14 is designed to produce a positional orspatial displacement predominately along one predetermined axis. Thefunction of the actuator 14 can be performed by one of several differenttypes of piezoelectric devices including an individual piezoelectricelement, a stack of individual piezoelectric elements, a mechanicallyamplified piezoelectric element or stack, or, preferably, a multilayercofired piezoelectric stack.

When a voltage is applied across the piezoelectric device, the devicereceives and stores an electrical charge. When charged, thepiezoelectric device expands predominately along the one predeterminedaxis. The expansion of the piezoelectric device produces a spatialdisplacement along the one predetermined axis increasing the initialuncharged thickness of the device. In this manner, the one predeterminedaxis functions as an axis of displacement. The amount of electricalcharge stored by the piezoelectric device is generally proportional tothe amount of voltage applied across the device up to a maximum voltagelimit. The amount of expansion along the one predetermined axis isgenerally proportional to the amount of electrical charge stored by thepiezoelectric device. Thus, the amount of expansion along the onepredetermined axis can be controlled by varying the amount of voltageapplied across the piezoelectric device. For example, applying themaximum amount of voltage across the piezoelectric device produces amaximum amount of expansion along the one predetermined axis andapplying one-half the maximum amount of voltage across the piezoelectricdevice produces approximately one-half the maximum amount of expansionalong the one predetermined axis.

The electrical charge on the piezoelectric device is discharged ordissipated when the device is (1) connected directly to ground, (2)electrically shorted directly across the terminal ends, or (3)electrically shorted or grounded through an impedance. When discharged,the piezoelectric device contracts or shrinks along the onepredetermined axis back toward the initial uncharged thickness of thedevice. The discharge of the piezoelectric device can be controlled toproduce a spatial displacement along the one predetermined axisdecreasing the thickness of the device.

The controller 28 is designed to operate the apparatus 10. To produce aspatial displacement along the predetermined axis, the controller 28provides a charging voltage across the piezoelectric device. Typically,the amount of spatial displacement is approximately proportional to thecharging energy. To return the piezoelectric device to the initialuncharged thickness, the controller 28 provides the necessary dischargemeans (i.e. the controlled electrical grounding or shorting) describedabove. The controller 28 is designed to completely charge and completelydischarge the piezoelectric device. As a result, the opposing surfaces22 and 24 of the apparatus 10 are maintained in either a fully open orfully closed position. The controller 28 can be designed to partiallycharge and partially discharge the piezoelectric device, if desired. Asa result, the opposing surfaces 22 and 24 of the apparatus 10 can bemaintained in the fully open position, the fully closed position, or anyposition therebetween (i.e any partially open or partially closedposition). The partial opening and closing of the opposing surfaces 22and 24 can be based directly on sensor feedback or on an algorithmprocessing such sensor feedback. The controller 28 can be furtherdesigned to recycle discharged power by storing power discharged fromthe piezoelectric device and reusing such power during the next chargingof the piezoelectric device. The controller 28 can also be designed tosupply such recycled discharged power to one or more other piezoelectricor non-piezoelectric devices.

FIG. 2 is a side view of the first embodiment of the apparatus 10.Preferably, the rigid, non-flexing portion 16 of the apparatus 10 isC-shaped including a rigid non-flexing web 30 extending between a pairof rigid non-flexing arm portions 32, 34. At least one pivotable armportion 18 is pivotably connected via a living integral hinge 36 to onerigid arm portion 32. Another pivotable arm portion 20 can optionally bepivotably connected via a living integral hinge 38 to the other rigidarm portion 34, if two opposing pivotable arms are desired. The forcetransfer member 26 includes a seat surface 40.

The actuator 14 includes opposite ends 42 and 44 and, as describedabove, the actuator 14 produces a controlled spatial displacementbetween the opposite ends 42 and 44 in response to an electricalactivation. One end 42 of the actuator 14, hereinafter referred to asthe set or fixed end 42, is disposed adjacent to the rigid web 30. Theother end 44 of the actuator 14, referred to hereinafter as the drivingend 44, is disposed adjacent to the seat surface 40 of the forcetransfer member. Thus, the actuator 14 is operably engaged between thenonflexing web 30 and the force transfer member 26 for driving the forcetransfer member 26 away or apart from the rigid web 30 in response to anelectrical activation of the actuator 14. In other words, thepiezoelectric device is oriented such that the axis of greatestdisplacement is aligned perpendicular to the web 30 and the seat surface40.

In FIG. 2, the actuator 14 is deactivated. The opposing surfaces 22 and24 are closest to each other when the actuator 14 is deactivated. Thistype of configuration is commonly referred to as a normally closeddesign. When the actuator 14 is electrically activated, the set end 42of the actuator 14 is held fixed by the rigid portion 16, the drivingend 44 of the actuator 14 drives the force transfer member 26 away orapart from the rigid web 30 (i.e. to the right in FIG. 2), and the firstand second pivotable arm portions 18 and 20 are pivoted about livingintegral hinges 36 and 38 respectively. In this manner, the space ordistance between the opposing surfaces 22 and 24 is increased. In otherwords, when a voltage is applied across the piezoelectric device, thespatial displacement produced along the predetermined axis drives theforce transfer member 26 away or apart from the rigid portion 16pivoting the first and second pivotable arm portions 18 and 20 about theliving integral hinges 36 and 38 respectively thus increasing the spaceor distance between the opposing surfaces 22 and 24. The opening of theopposing surfaces 22 and 24 can be adjusted by varying the amount ofvoltage applied across the piezoelectric device.

The support 12 is composed of a material having shape memory. Typically,the support material has a high modulus of elasticity and high strength.As a result, the apparatus 10 can be made from a variety of materialsincluding, but not limited to, a metal, such as steel or other metals,an alloy, such as Inconel or other alloys, or a composite material, suchas Thornel.

When the actuator 14 is deactivated, the opposing surfaces 22 and 24 arebiased toward one another by the shape memory of the support structurematerial provided the support 12 has not been plastically deformed. Inother words, when the piezoelectric device is discharged, thepiezoelectric device shrinks or contracts along the axis of expansionand the shape memory of the support structure material biases the forcetransfer member 26, the first and second pivotable arm portions 18 and20, and the opposing surfaces 22 and 24 back toward the original shapeof the apparatus 10. The closing of the opposing surfaces 22 and 24 canbe adjusted by controlling the discharge of the piezoelectric device.

The present invention maximizes the transfer of force from the expansionof the actuator 14 through the force transfer member 26 to the pivotingof the pair of pivotable arm portions 18 and 20 and the opening of theopposing surfaces 22 and 24. For maximum force transfer, the set end 42of the actuator 14 is fixed by the rigid portion 16. In other words, theapparatus 10 is designed so the rigid portion 16 does not flex or bowwhen the actuator 14 is activated. In this manner, all of the actuatorexpansion force is directed through the driving end 44 of the actuator14 toward the force transfer member 26. To transfer the maximum forcefrom the actuator 14 to the pair of pivotable arm portions 18 and 20,the force transfer member 26 is designed so that the seat surface 40does not flex or bow when the actuator is activated. The driving end 44of the actuator 14 remains in operable contact or optimal forcetransferring contact with the seat surface 40 of the force transfermember 26 at all spatial displacements of the actuator 14, i.e. at theminimum operating spatial displacement, the maximum operating spatialdisplacement, and all spatial displacements of the actuatortherebetween. In other words, the driving end 44 of the actuator 14remains in operable contact or optimal force transferring contact withthe seat surface 40 of the force transfer member 26 when the actuator isdeactivated, partially activated, and fully activated.

In the first embodiment of the apparatus 10, the driving end 44 of theactuator 14 has a planar surface and the seat surface 40 of the forcetransfer member 26 is a planar surface with the planar end surface 44 ofthe actuator 14 disposed adjacent to the planar seat surface 40 of theforce transfer member 26. FIG. 2 illustrates the planar driving end 44of the actuator 14 in operable contact with the planar seat surface 40of the force transfer member 26 when the actuator is deactivated. FIG. 3illustrates the planar driving end 44 of the actuator 14 in operablecontact with the planar seat surface 40 of the force transfer member 26when the actuator 14 is partially activated and is exaggerated to show alarger opening between the opposing surfaces 22,24 than would normallybe seen. FIG. 4 is also exaggerated to illustrate the planar driving end44 of the actuator 14 in operable contact with the planar seat surface40 of the force transfer member 26 when the actuator 14 is fullyactivated and shows a larger opening between the opposing surfaces 22,24than would actually be seen in the fully activated position.

FIG. 5 is a second embodiment of the apparatus 10 a with the forcetransfer member 26 a having an alternative T-shape. The apparatus 10 aincludes a support 12 a and an actuator 14 a similar to that previouslydescribed for the other embodiments. The support 12 a includes a rigidnon-flexing portion 16 a, at least one pivotable arm portion 18 a, 20 aextending from the rigid non-flexing portion 16 a, a pair of opposingsurfaces 22 a, 24 a with one opposing surface 22 a, 24 a on eachpivotable arm portion 18 a, 20 a for movement relative to one another,and a force transfer member 26 a operably positioned between the firstand second pivotable arm portions 18 a, 20 a. Preferably, as with theother embodiments the entire support 12 a is formed as a unitary,integral, single-piece body. The actuator 14 a is operably engagedbetween the rigid portion 16 a and the force transfer member 26 a todrive the force transfer member 26 a in linear motion away from therigid web 30. Movement of the force transfer member 26 a pivots thefirst and second pivotable arm portions 18 a, 20 a about the livingintegral hinges 36 a, 38 a respectively. A controller (not shown) can beprovided to operate the apparatus 10 a. The controller can provide acharging voltage across a piezoelectric device to produce spatialdisplacement along a predetermined axis as previously described for theother embodiments. The rigid portion 16 a of the apparatus 10 a caninclude a C-shaped web 30 a extending between a pair of rigid armportions 32 a, 34 a. One pivotable arm portion 18 a is pivotablyconnected via the living integral hinge 36 a to one rigid non-flexingarm portion 32 a, and the other pivotable arm portion 20 a is pivotableconnected via the living integral hinge 38 a to the other rigidnon-flexing arm portion 34 a. The force transfer member 26 a can includea seat surface 40 a. The actuator 14 a includes opposite ends 42 a and44 a. The actuator 14 a produces a controlled spatial displacement alongthe predetermined axis between opposite ends 42 a and 44 a in responseto an electrical activation. One end 42 a of the actuator 14 a, such asa set or fixed end 42 a, is disposed adjacent to the rigid web 30 a. Theother end 44 a of the actuator 14 a, such as a driving end 44 a, isdisposed adjacent to the seat surface 40 a of the force transfer member26 a. When the actuator 14 a is electrically activated, the set end 42 aof the actuator 14 a is held fixed by the rigid portion 16 a, thedriving end 44 a of the actuator 14 a drives the force transfer member26 a away or apart from the rigid portion 16 a (i.e. to the right inFIG. 5), and the first and second pivotable arm portions 18 a, 20 a arepivoted about the living integral hinges 36 a, 38 a respectively, with aloss of motion of less than 40%. In this configuration, the forcestransferred from the force transfer member 26 a to the pivotable armportions 18 a, 20 a are transmitted through force transfer webs orhinges 48 a, 50 a extending between the force transfer member 26 a andthe corresponding pivotable arm portions 18 a, 20 a. The line of forcetransfer is generally parallel to the predetermined axis of spatialexpansion of the piezoelectric actuator 14 a, and preferablyperpendicular to the fulcrum axis or axis of rotation of the pivotablearm portions 18 a, 20 a about the corresponding living integral hinges36 a, 38 a.

FIG. 6 is a third embodiment of the apparatus 10 b with an adjustableseat 52 b supported by the rigid portion 16 b with an adjustable support54 b. The apparatus 10 b includes a support 12 b and an actuator 14 bsimilar to that previously described for the other embodiments. Thesupport 12 b includes a rigid non-flexing portion 16 b, at least onepivotable arm portion 18 b, 20 b extending from the rigid non-flexingportion 16 b, a pair of opposing surfaces 22 b, 24 b with one opposingsurface 22 b, 24 b on each pivotable arm portion 18 b, 20 b for movementrelative to one another, and a force transfer member 26 b operablypositioned between the first and second pivotable arm portions 18 b, 20b. Preferably, as with the other embodiments the entire support 12 b isformed as a unitary, integral, single-piece body. The actuator 14 b isoperably engaged between the rigid portion 16 b and the force transfermember 26 b to drive the force transfer member 26 b in linear motionaway from the rigid portion 16 b. The rigid portion 16 b supports withan adjustable support 54 b an adjustable seat 52 b having acomplementary surface to the end 42 b of the actuator 14 b. Thecomplementary surface of the adjustable seat 52 b can be flat or shapedin any manner to support the actuator 14 b in a position suitable fordriving the force transfer member 26 b in response to electricalactuation of the actuator 14 b. Movement of the force transfer member 26b pivots the first and second pivotable arm portions 18 b, 20 b aboutthe living integral hinges 36 b, 38 b respectively. A controller (notshown) can be provided to operate the apparatus 10 b. The controller canprovide a charging voltage across a piezoelectric device to producespatial displacement along a predetermined axis as previously describedfor the other embodiments. The rigid portion 16 b of the apparatus 10 bcan include a web 30 b extending between a pair of rigid arm portions 32b, 34 b. One pivotable arm portion 18 b is pivotably connected via theliving integral hinge 36 b to one rigid arm portion 32 b, and the otherpivotable arm portion 20 b is pivotable connected via the livingintegral hinge 38 b to the other rigid arm portion 34 b. The forcetransfer member 26 b can include a seat surface 40 b. The actuator 14 bincludes opposite ends 42 b and 44 b. The actuator 14 b produces acontrolled spatial displacement along the predetermined axis betweenopposite ends 42 b and 44 b in response to an electrical activation. Oneend 42 b of the actuator 14 b, such as a set or fixed end 42 b, isdisposed adjacent to the rigid web 30 b as shown in the previousembodiments, or supported by the adjustable seat 52 b connected to therigid web 30 b. The other end 44 b of the actuator 14 b, such as adriving end 44 b, is disposed adjacent to the seat surface 40 b of theforce transfer member 26 b. When the actuator 14 b is electricallyactivated, the set end 42 b of the actuator 14 b is held fixed by theadjustable seat 52 b connected to the rigid portion 16 b, the drivingend 44 b of the actuator 14 b drives the force transfer member 26 b awayor apart from the rigid portion 16 b (i.e. to the right in FIG. 6), andthe first and second pivotable arm portions 18 b, 20 b are pivoted aboutthe living integral hinges 36 b, 38 b respectively, with a loss ofmotion of less than 40%. In this configuration, the forces transferredfrom the force transfer member 26 b to the pivotable arm portions 18 b,20 b are transmitted through force transfer webs or hinges 48 b, 50 bextending between the force transfer member 26 b and the correspondingpivotable arm portions 18 b, 20 b. The line of force transfer isgenerally parallel to the predetermined axis of spatial expansion of thepiezoelectric actuator 14 b, and preferably perpendicular to the fulcrumaxis or axis of rotation of the pivotable arm portions 18 b, 20 b aboutthe corresponding living integral hinges 36 b, 38 b. It should berecognized that the adjustable support 54 b and complementary seat 52 billustrated in FIG. 6 can be used in the other embodiments illustratedin FIGS. 1-5 without departing from the spirit and scope of the presentinvention.

Referring now to the invention in general, the apparatus according tothe present invention is based on mechanical conversion of the motionand force of the actuator by means of the force transfer member. Theactuator is preferably a solid state device that increases its size inone or more dimensions when electrically or magnetically stimulated. Anexample of such a device is a cofired piezoelectric stack. Further, thedevice preferably has a rectangular prism geometry. The actuator isdisposed within the body cavity of the support. The body cavity isbounded on one side by the inside surface of the rigid non-flexing weband on the other side by the inside surface of the moveable forcetransfer member. The body cavity is further bounded by the upper insidesurface of the support defined by the rigid non-flexing arm portion andthe opposing lower inside surface of the support defined by the rigidnon-flexing arm portion. The actuator is mounted within the body cavityso that one face or end of the actuator is in direct contact with theinside surface of the web, while the opposing face or end of theactuator is in direct contact with the inside surface of the forcetransfer element. In other words, the actuator is under continuouscompression from the inside surface of the web and the inside surface ofthe force transfer element. If desired, an adjustable rigid non-flexingsupport member can be connected to the web for adjustably supporting theone face of the actuator in compression against the opposing face of theforce transfer element.

The actuator is actuated by application of appropriate electrical power.The electrical power is controlled by a controller similar to thatillustrated as 28 in FIG. 1. The controller, in its simplest form, canbe a switching device. The controller is connected to the actuator viaelectrical wires. The controller can have multiple embodiments. Forexample, it can be designed to fully actuate and fully deactuate theactuator. It can be designed to actuate the actuator to any incrementbetween fully extended and fully retracted. It can also be designed toreuse or redirect the power in the actuator to optimize efficiency.

When the actuator is deenergized or unactuated, it is at a rest positionwith initial uncharged dimensional conditions. When energized oractuated, the actuator expands along one or more axes as determined bythe material properties of the actuator. This expansion is due to thepiezoelectric, electrorestrictive, or magnetorestrictive phenomenondepending on the type of actuator actually used in a specific embodimentof this invention. The actuator is designed so that the spatialdimension of maximum expansion when actuated is in line with the twobounding inside surfaces of the web and the force transfer member. Sincethe actuator is under compression by the two bounding inside surfaces ofthe web and force transfer member, when the actuator is electricallyactuated and expands along the primary expansion axis, the actuator willexert additional pressure against the two bounding inside surfaces.

The web is designed to provide a rigid structure for the actuator topush directly against, or indirectly against through the adjustableseat. Since the web constrains the actuator, the force transfer element,which is designed to move within the apparatus, is displaced by theexpanding actuator. The force transfer element in turn is connected viaintegral hinges or webs, to the upper pivotable arm and the lowerpivotable arm. The force transfer element is connected to the upper andlower arms with webs, and the integral hinges divide the pivotal armportions from the rigid arm portions of the support. Both rigidnon-flexing arm portions serve as structural members integral with therigid non-flexing web. The hinges are designed so that the force anddisplacement generated by the piezoelectric element travel through theforce transfer element and are focused and applied extremely close tothe fulcrum of the hinges. Therefore, the force transfer elementtransfers a substantial portion of the force and displacement of theexpanding actuator to the pivotable arms through the webs. The apparatusis designed so that the expansion of the actuator causes the upper andlower pivotable arm portions to pivot outward about the integral hingesso that the face of one of the pivotable arm separates from the face ofthe other pivotable arm with a loss of motion of less than 40%.Deactuation of the actuator restores the spatial displacement of theforce transfer element to the initial position along the predeterminedaxis. This in turn causes the overall structure of the support to revertto the initial or rest state.

The piezoelectric actuator is preferably preloaded with force wheninstalled in the support. If desired, the piezoelectric actuator can beclamped within the support with an adjustable seat positioned betweenthe rigid non-flexing web and one end of the actuator. By way of exampleand not limitation, an adjustable screw configuration can be used forthis purpose, or any other suitable arrangement allowing for optimalforce preloading on the piezoelectric actuator can be provided.Preloading contributes to maximum efficiency of force transfer from thepiezoelectric actuator to the support during actuation. Preloading alsoallows fine tuning of the initial, uncharged position of the apparatusaccording to the present invention. Proper preloading ensures that thepiezoelectric actuator remains in contact with the support at both endsduring the full range of expansion and contraction without requiring theuse of adhesive or other measures to secure the piezoelectric actuatorto the support. Preloading also helps to avoid the possibility ofsubjecting the piezoelectric actuator to undesirable tension ortorsional moments, which could cause damage. An adjustable seat for oneend of the piezoelectric actuator allows for simple compensation ofdimensional variations of the piezoelectric actuator during assembly ofthe apparatus.

The present invention is disclosed and discussed in detail with respectto at least one pivotable arm portion, and preferably two opposingpivotal arm portions. It should be recognized that the present inventionincludes both symmetrical and asymmetrical movement of the pivotal armportions. If desirable, the integral hinges can be provided to providenon-symmetric operation of at least one pivotable arm portion. By way ofexample and not limitation, this type of movement can be desirable insome valving or clamping configurations.

Referring now to FIG. 7, a simplified flow chart illustrates theoptimization of the orientation of the hinge members of the mechanicalsupport according to the present invention. Beginning at step 100, therequirements of the application are defined. The requirements can be aselection of parameters, by way of example and not limitation, includingthe parameters of force, displacement, size, operating frequency, cyclelife, temperature, operating voltage, operating power, vibration, impactresistance, environmental resistance, corrosion resistance, productioncost, hysteresis, linearity, and/or repeatability. After therequirements are defined in step 100, the process continues to step 102where specifications and preliminary geometry of the mechanical supportare developed. The process then continues to step 104 where twodimensional (2D) static stress analysis is performed to optimize thehinge geometry of the mechanical support. A three dimensional (3D)computer aided design (CAD) model is then designed in step 106 based onthe optimized geometry obtained in step 104. Finite element stressanalysis (FEA) is then conducted in step 108 to predict performance ofthe mechanical support and piezoelectric element. In conducting theanalysis, it has been found useful to apply 20% of the maximum force ofthe piezoelectric element to the force arms for one series of analysis.It has also been found useful to run a series of analysis whileconstraining the arms of the mechanical support and applying force tothe force transfer element to determine the force available from thepivotable arms with no displacement. As a result of the finite elementstress analysis separate curves are developed of force versusdisplacement for the mechanical support and the piezoelectric element.These curves are graphed on the same common axes in step 110 todetermine if an intersection of the curves occurs. By way of example andnot limitation, one set of these curves is illustrated in FIG. 8, wherethe piezoelement curve is labeled 122 and the mechanical support curveis labeled 124. FIG. 8 illustrates an exemplary intersection of the twocurves 122,124 at the point labeled 126. The identification of theintersection of the curves occurs in step 112. In query 114, it isdetermined if the intersection satisfies the force and displacementrequirements previously set in step 100. If the requirements are notsatisfied, the process branches back to step 102, where the model can bemodified and reanalyzed. If the requirements are satisfied, the processbranches to step 116. In step 116, the finite element stress analysis isperformed again using the values corresponding to the point 126 ofintersection of the two curves 122, 124. The process then proceeds toquery 118 to determine if the performance is verified against theapplication requirements selected in step 100. If the performance is notverified, the process branches back to step 102, where the model can bemodified, and reanalyzed. If the performance is verified, the processends at step 120.

The apparatus is designed using finite element analysis to meet severalcriteria. The support must provide repeated operation. Operating life inexcess of 100 million cycles can reasonably be expected. For a givenactuator, the length of the pivotable arm portions, and the geometry ofthe integral hinges can be designed to provide varying amounts ofseparation of the faces.

A characteristic of this invention is that the force transfer element,the hinges, the pivotable arm portions, the rigid arm portions, and theweb are an integral, single, unitary, or monolithic body. That is, thereare no fasteners joining these components. Elimination of the fasteningmethods results in highly efficient transfer of force and displacementfrom the actuator to the support.

Another characteristic of the support of the present invention is thatthe actuator is oriented so that the primary axis of expansion is at aright angle with respect to the axis of pivot of the pivotable arms.This characteristic is beneficial in several respects. Foremost is thatit enables a hinge geometry where the force application point from theforce transfer element can be extremely close to the fulcrum of thehinges. This enables the ability to maximize the force transferefficiency. An additional advantageous result of this geometry is thatit enables a compact overall design of the apparatus. A further benefitis that the geometry is readily supportive of size scaling fromapproximately less than 1 cubic inch to approximately 20 cubic inches.This scalability in size provides the design envelope for a broad rangeof displacements from approximately {fraction (1/10,000)} inch toapproximately 0.25 inches. Similarly, the geometry provides for a widerange of clamping forces from less than 1 pound to more than 100 pounds.Yet another benefit is that the entire surface of both faces of thepiezoelectric element remain in compressed contact with the opposingfaces of the support structure; namely, the rigid web 30 at one end andthe force transfer element 26 at the opposite end.

In the embodiments illustrated in FIGS. 1-6, these components have beenmachined from a single piece of metallic material for example stainlesssteel. Other suitable materials can include powdered metal, metallicalloys, composite materials, or a combination of metallic and compositematerials. Although these materials given as examples provide excellentperformance, depending on the requirements of a particular application,use of other materials for the support can be appropriate.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiments but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims, which scope is to be accorded the broadestinterpretation so as to encompass all such modifications and equivalentstructures as is permitted under the law.

1. A method for optimizing hinge geometry comprising the steps ofconducting finite element stress analysis on a three dimensional modelof hinge geometry for a support structure operably engagable with apiezoelectric actuator to predict performance; analyzing separate curvesfor force versus displacement for the support and the piezoelectricactuator; and identifying an intersection of the separate force versusdisplacement curves to optimize hinge geometry.
 2. The method of claim 1further comprising the steps of: determining if the intersection of thecurves satisfies the predefined force and displacement requirements; ifthe intersection of the curves does not satisfy the predefined force anddisplacement requirements, returning to the designing step; if theintersection of the curves does satisfy the predefined force anddisplacement requirements, conducting finite element stress analysis ofthe three dimensional model using values corresponding to theintersection of the curves; determining if performance of the threedimensional model with finite element stress analysis using valuescorresponding to the intersection of the curves is verified againstapplication requirements; and if performance is not verified, returningto the developing step.
 3. The method of claim 1 further comprising:developing preliminary geometry based on defined force and displacementrequirements; and performing two dimensional stress analysis to optimizeorientation of hinge geometry.
 4. The method of claim 1 furthercomprising the step of: designing a three dimensional model of hingegeometry for a support structure to operably engage a piezoelectricactuator.
 5. An apparatus according to the method of claim 1 for movingat least one of a pair of opposing surfaces in response to an electricalactivation comprising: a support including a rigid non-flexing portion,at least one pivotable arm portion extending from the rigid portion, apair of opposing surfaces with one opposing surface on the at least onepivotable arm portion for movement relative to one another, and a forcetransfer member operably positioned for driving the at least onepivotable arm portion in rotational movement; and an actuator operablyengaged between the rigid portion and the force transfer member to drivethe force transfer member relative to the rigid portion to pivot the atleast one pivotable arm portion in response to an electrical activationof the actuator.
 6. The apparatus of claim 5 wherein the support is asingle piece.
 7. The apparatus of claim 5 wherein the actuator is apiezoelectric device.
 8. The apparatus of claim 5 wherein the rigidportion is C-shaped including a web extending between a pair of rigidarm portions.
 9. The apparatus of claim 8 wherein one of the pivotablearm portions is pivotably connected to one of the rigid arm portions andthe other of the pivotable arm portions is pivotably connected to theother of the rigid arm portions.
 10. The apparatus of claim 5 whereinthe actuator includes opposite ends and produces a spatial displacementbetween the opposite ends in response to an electrical activation. 11.The apparatus of claim 10 wherein the rigid portion supports a seatsurface.
 12. The apparatus of claim 11 wherein one of the opposite endsof the actuator is a planar surface and the seat surface supported bythe rigid portion is a planar surface with the planar end surface of theactuator disposed adjacent to the planar seat surface supported by therigid portion.
 13. The apparatus of claim 12 wherein the planar endsurface of the actuator applies force to the planar seat surfacesupported by the rigid portion in response to a spatial displacement ofthe actuator.
 14. The apparatus of claim 13 wherein the planar endsurface of the actuator operably contacts the planar seat surfacesupported by the rigid portion at a minimum operating spatialdisplacement of the actuator.
 15. The apparatus of claim 13 wherein theplanar end surface of the actuator operably contacts the planar seatsurface supported by the rigid portion at a maximum operating spatialdisplacement of the actuator.
 16. The apparatus of claim 13 wherein theplanar end surface of the actuator operably contacts the planar seatsurface supported by the rigid portion at all spatial displacementsbetween a minimum operating spatial displacement of the actuator and amaximum operating spatial displacement of the actuator.
 17. Theapparatus of claim 5 wherein the force transfer member includes a seatsurface.
 18. The apparatus of claim 17 wherein one of the opposite endsof the actuator is a planar surface and the seat surface of the forcetransfer member is a planar surface with the planar end surface of theactuator disposed adjacent to the planar seat surface of the forcetransfer member.
 19. The apparatus of claim 18 wherein the planar endsurface of the actuator applies force to the planar seat surface of theforce transfer member in response to a spatial displacement of theactuator.
 20. The apparatus of claim 19 wherein the planar end surfaceof the actuator operably contacts the planar seat surface of the forcetransfer member at a minimum operating spatial displacement of theactuator.
 21. The apparatus of claim 19 wherein the planar end surfaceof the actuator operably contacts the planar seat surface of the forcetransfer member at a maximum operating spatial displacement of theactuator.
 22. The apparatus of claim 19 wherein the planar end surfaceof the actuator operably contacts the planar seat surface of the forcetransfer member at all spatial displacements between a minimum operatingspatial displacement of the actuator and a maximum operating spatialdisplacement of the actuator.
 23. The apparatus of claim 5 wherein therigid portion, the pivotable arm portion and the force transfer membermeet at one location to form a force transfer mechanism.
 24. Theapparatus of claim 6 further comprising an integral spring defined whereat least one pivotable portion attaches to the rigid portion.